This invention relates to check valves and, more particularly, to a controlled action check valve wherein the closing of the check valve is retarded to prevent slamming.
Most check valves that are of the medium and large size as used by the petroleum production industry are constructed in the form of a clapper pivotally mounted on a shaft over a seat contained in an enlarged portion of the flow line. The clapper is free to pivot open if fluid is flowing in one direction, but if fluid begins to flow in the opposite direction the clapper will close and seal the flow line to prevent further reverse flow. Hydraulic control systems for such check valves have previously been disclosed as shown in the Camp patent incorporated by reference. Camp uses a hydraulic cylinder connected through a crosshead and a rod to the clapper portion of the check valve. The hydraulic cylinder has restrictive flow of fluid from below a piston contained therein to above the piston and vice/versa. An accumulator keeps the hydraulic cylinder recharged with a sufficient amount of fluid. The pressure of the fluid contained in the hydraulic cylinder is equal to the pressure in the pipeline due to interconnecting passages between the crosshead and the accumulator.
The incorporated Elliot patent shows a hydraulic control portion wherein the pressure on the hydraulic fluid was supposed to be very low. In Elliot, again a piston in a hydraulic cylinder was connected through a crosshead to the clapper by means of a connecting rod. Also in Elliot the piston rod which connects to the crosshead is extended through the top portion of the hydraulic cylinder thereby preventing a need for large amounts of fluid to flow from below the piston to above the piston and vice/versa because the same volume area of the piston rod is always inside the hydraulic cylinder. Elliot also included a rifle drill passage in the piston rod to bleed any air out of the hydraulic cylinder upon installation or repairs of that apparatus. Both of these prior incorporated patents had disadvantages that are not included in the present invention as will be described in more detail hereinafter.